1. Field of Invention
The present invention relates to an electrical junction box suitable to be connected, for example, to a wire harness in a vehicle, such as an automobile.
2. Description of Related Art
Recently, the increase of electrical and electronic component parts which are mounted in a vehicle has led to increase of circuits to be accommodated in electrical connection boxes and junction boxes in the vehicle. Thus, when forming branch circuits at a high density, it is necessary to mount a large number of component parts on a junction box, or the like, which causes increase of manufacturing complexity.
In a junction box disclosed in JP-A-2000-92660 and shown in present FIG. 19, bus bars 5A-5D are laminated one upon another between an upper case part 2 and a lower case part 3, with insulation plates 4A-4E interposed between the bus bars 5A-5D. The upper case part 2 has a connector receiving portion 2a, a relay receiving portion 2b, and a fuse receiving portion 2c, on which in use connectors 6, relays 7 and fuses 8 are mounted, respectively. Terminals of the connectors 6, the relays 7 and the fuses 8 are connected to tabs 5a projecting from the bus bars directly or are connected to the bus bars through relaying terminals. The lower case part 3 has also a connector receiving portion 3a to connect connectors to tabs projecting from the bus bars.
In the junction box 1, with the increase of the number of circuits, the area and the number of layers of the bus bars increase and thus the size of the junction box becomes large. If the connector, relay and fuse receiving portions are arranged on both the upper and lower case parts to connect connectors, relays and fuses to internal circuits of the junction box, it is possible to make the area of the junction box smaller than in the case where the receiving portions are mounted on only the upper case part or the lower case part.
However, if the connector, relay and fuse receiving portions are mounted on both the upper and lower case parts such that they are opposed vertically, the bent tabs of bus bars must overlap each other and thus cannot be easily arranged. In this case, it is necessary to form tabs on bus bars of other layers, which causes an increase of number of layers of bus bars, and thus leads to the increase of the height of the junction box. That is, the junction box is necessarily large.
Further, the above-described junction box is so constructed that the bus bars are connected to the connectors, the fuses and the relays. Thus, when the specification of the connection between the internal circuit and the fuses and/or the relays is altered, it is necessary to alter the entire internal circuit. Consequently, the above-described junction box is incapable of allowing a circuit alteration easily.
Some proposals have been made for replaceable modules in electrical circuits of automobiles.
U.S. Pat No. 5,179,503 shows a modular automobile power distribution box having replaceable modules carrying relays or fuses. The relays or fuses in each module are directly connected to terminals of leads of wire harnesses. A pair of bus bars connect power terminals to the fuses of three maxi-fuse modules. There is no discussion of interconnection of the modules.
U.S. Pat. No. 5,581,130 discloses removable multi-function modules in individual casings which are mounted on a circuit board. Each module is electrically connected to the power supply distribution layer of the board by a pin. Alternatively, three modules are shown connected together by two electrical and mechanical coupling bars.
It is an object of the present invention to provide a junction box which can be made thin and can keep to a minimum the number of layers of bus bars accommodated in the junction box and which can permit a circuit alteration easily.
According to the present invention, there is provided an electrical junction box adapted to provide electrical connection to a plurality of electrical connectors, a plurality of fuses and a plurality of relays, having
(i) upper and lower case parts joined together to provide a casing;
(ii) a base circuit having a plurality of first bus bars and insulation layers stacked together with said insulation layers interposed between the bus bars in a stacking direction, a base circuit being mounted in the casing and the first bus bars being arranged to provide electrical connection to electrical connectors in use;
(iii) a fuse circuit having a fuse circuit substrate, which is discrete from the base circuit, and a plurality of second bus bars fixed on the fuse circuit substrate, the fuse circuit being mounted in the casing and said second bus bars being arranged to provide electrical connection to fuses in use; and
(iv) a relay circuit having a relay circuit substrate, which is discrete from the base circuit, and a plurality of third bus bars fixed on the relay circuit substrate, the relay circuit being mounted in the casing and the third bus bars being arranged to provide electrical connection to relays in use;
(v) wherein the second bus bars and the third bus bars are joined to the first bus bars by welding.
In the junction box of the present invention described above, the first bus bars of the base circuit are provided separately from the second bus bars for fuses and the third bus bars for relays by dividing the circuits, and are joined by welding. The respective substrates are discrete, i.e. separate elements in the casing, as shown in the embodiments below. This is in contrast with the conventional method, in which electrically conductive sheets are punched to form unitarily the connector connection circuit, the fuse connection circuit, and the relay connection circuit and form tabs to be connected to connectors, tabs to be connected to fuses, and tabs to be connected to relays, and stacked in a single stack, the circuits thus being handled and arranged in a complicated manner, which causes increase of the area of the bus bars and the use of a large number of the bus bars. On the other hand, according to the present invention, because the circuits are divided and welded, it is possible to avoid the complication of tabs overlapping each other and avoid a large number of bus bars. Thus, it is possible to form a thin or compact junction box. Further, because the circuits of the bus bars can be arranged and disposed easily, the area of each bus bar can be reduced. Consequently, even though the bus bars are separately provided for the connector connections on the one hand and the fuse connections and the relay connections on the other hand, it is possible to reduce the total area of the bus bars and avoid increase of the area of the junction box.
In one form of the invention, the fuse module having the fuse connection circuit and the relay module having the relay connection circuit are separately provided, i.e. on discrete substrates. Thus, if any feature of the specification of the fuse and the relay is altered, only the fuse module or the relay module needs to be changed to produce a different design of box. That is, the construction can permit alteration of the specification easily. On the other hand, if the specification of a connector connection is altered, only the base circuit is changed. Thus, the construction can cope with a circuit alteration easily.
In an alternative construction, it is possible to combine the fuse module and the relay module with each other to form a fuse/relay composite module which receives fuses and relays on the same substrate which has bus bars for fuses and relays on it. In this case, if it is necessary to connect the circuit of any of the bus bars for fuses to any of the bus bars for relays, the respective bus bars are welded to each other or bars may be integrally formed.
Terminals of the first bus bars may be disposed in sockets of a connector receiving portion formed in the upper case part and/or the lower case part directly or through relaying terminals. Fuse-mounting sockets on a member carried on the substrate of the fuse module and/or relay-mounting sockets on a member carried on the substrate of the relay module may be exposed to the exterior of the upper case part and/or the lower case part through openings. This allows fuses and relays to be installed and replaced from the outside. For example, an opening is formed at one side of the upper case part to expose the fuse-mounting sockets and another opening is provided to expose the relay-mounting portion at one side of the lower case.
Alternatively, fuse-mounting sockets and/or relay mounting sockets may be provided integrally on the case parts, e.g. with terminals of the bus bars projecting into these sockets.
The second bus bars and third bus bars may thus individually be directly connected to terminals of fuses and terminals of relays, respectively.
Preferably, each second bus bar and each third bus bar has a terminal portion formed by bending a horizontal portion thereof upward at one end of the horizontal portion which is fixed to the respective substrate and a pressure contact groove is formed at the end of the terminal portion thereof to allow a terminal of a fuse or a relay to be connected thereto under pressure. The other end of the horizontal portion of each bus bar may be welded to one of the first bus bars. This construction allows the second and third bus bars to be connected to fuses and relays without using relaying terminals.
The first bus bars may be welded to the welding portions of the second bus bars and/or the third bus bars by any suitable method, such as ultrasonic welding, resistance welding, laser welding or gas welding. Preferably, the portions which are welded project externally from the insulation layers and the respective substrate.
Use of such welding techniques does not reduce reliability of the electrical connection. By arranging the welded portions parallel with one another, ultrasonic welding, resistance welding, laser welding or gas welding can be efficiently accomplished. The bus bar portions are, for example, welded to each other by layering them on each other horizontally or by bending them vertically and locating them alongside each other vertically. It is possible to connect the connector connection bus bars to the fuse connection bus bars and the relay connection bus bars by means of fit-in of male and female terminals.
The bus bars of the base circuit and the insulation layers are alternately laminated on each other inside the upper and lower case parts. When accommodating an electronic control unit in the upper and lower case parts, preferably, the welded joints of the first bus bars to the second bus bars and/or the third bus bars are located in a dead space located below the electronic control unit.
The upper and lower case parts may accommodate a circuit consisting of electric wires and pressure contact terminals and/or a circuit of an FPC, PCB or the like.